In the past decade a variety of electronic devices, including portable electronic devices have come into wide spread use. In the design of electronic devices that are portable, emphasis is placed on reducing the space occupied by each individual component, and reducing the cost.
Given the rapid introduction of these new types of portable electronic devices (e.g., Personal Digital Assistants, Text messaging pagers, MP3 players, cell phones), and the rapid development of novel functionality, an important objective in designing electronic devices is to provide intuitive user interfaces. Computer mouse-like keys and qwerty keyboards are some examples providing intuitive interfaces. However, these interfaces are directed more at providing input to the electronic device rather than providing content related feedback to a user. Touch screens along with graphical user interfaces (GUI) provide information to the user, but only if the user is looking at the screen.
Devices more recently are actively responding to user input by providing tactile cues or responses to the user. The vibrator in a cell phone or pager is a good example. Other examples include an input key that provides a clicking sound when moved; a key or touch screen that moves suddenly or vibrates in an opposed direction to the input; and a key that moves suddenly or vibrates perpendicular to the direction of input in response to a transducer attached to the device housing. However, all the devices mentioned here are implemented such that the component which supplies the sudden movement or vibration is mounted on the device housing, causing a vibration in the housing and resulting in a reduced or confusing sensation to the user. Thus, these implementations are limited in the amount of information they can provide.